Matrix remodeling and stromal-epithelial cellular communication contribute to aggressive progression of prostate cancer. Hyaluronan (HA), is a glycosaminoglycan polymer synthesized and turned over when appropriate for cell proliferation and motility. Normally, its levels are tightly controlled by HA synthase enzymes (HAS), hyaluronidases, and specific HA receptors such as the HA receptor for endocytosis (HARE). HA is negligible in normal adult prostate, but abundant in prostate tumors and bone metastases. Quantification of tumor cell associated HA and its turnover enzyme, Hyal1, predicts invasive progression and biochemical recurrence after resection. This proposal is focused on determining how the HA synthesis and turnover enzymes work together to influence matrix morphology and cell communication. The hypothesis is that surface HA borne by tumor cells increases metastatic efficiency by facilitating arrest in HARE-expressing vasculature and/or entry of the tumor cells into lymph and marrow tissue. In addition, excess tumor-borne HA may accelerate tumor cell endocytosis and/or endocytic recycling if Hyal1 is present, activating lymphatic remodeling. Rate of endocytic recycling determines the surface density of growth factor and adhesion receptors and thereby impacts tumor cell motility and metastatic survival. In aim 1, tumor cells selected for inducible HA synthesis or HA turnover will be used to test respective roles of these enzymes in clinically relevant mouse models of prostatic growth and bone metastasis. Pharmacological agents and in vivo knockdown will be used to examine how HARE functions in host target tissues to regulate prostate tumor cell colonization. These strategies will also determine how HA signaling and turnover may be therapeutically targeted to delay or prevent prostate cancer progression. Aim 2 will examine metastasis mechanisms by comparing the effects of tumor versus stromal components of HA metabolism and HA signaling on lymphatic vessel morphology, as well as lymph node and bone metastasis. The molecular format for delivery and propagation of the HA signals that trigger morphological changes to support metastasis will be characterized. Aim 3 will pursue the novel observation that elevated Hyal1, which is both a secreted and a lysosomal enzyme, increases the rate of endocytic recycling in the prostate tumor cells stably selected for its expression. The working hypothesis is that Hyal1 impacts several specific signaling pathways concurrently by modulating the rate of vesicular trafficking, thus contributing to tumor growth by maintaining surface presentation of important receptors and by re-externalizing biologically potent digestion products of HA that serve as signals. Its autocrine effects, as well as its impact on prostate stromal cells, will be tested.